1. Field of the Invention
The invention relates to a pneumatic hand tool, more particularly to a pneumatic hammer drill.
2. Description of the Related Art
Referring to FIG. 1, a conventional pneumatic hammer drill includes a handle body 1, a pneumatic cylinder 2, an air valve 202, and a tool 4. The handle body 1 has an upper portion 102 defining a cavity 101, and a lower grip portion 103 provided with an air inlet (not shown). The pneumatic cylinder 2 is fitted partially into the cavity 101, and includes a front tool-connecting end 201, a pressure chamber 203, a spring element 204 fitted around the front tool-connecting end 201, a piston 3 inserted slidably into the pressure chamber 203, and an air passage 205 in fluid communication with the pressure chamber 203 and the air valve 202. Highly compressed air is introduced into the air passage 205 via the air inlet in the handle body 1. The air valve 202 is disposed in the cavity 101 adjacent to the pneumatic cylinder 2. The tool 4 is inserted fittingly into the pressure chamber 203 through the front tool-connecting end 201.
In use, an operator holds the lower grip portion 103 of the handle body 1 with one hand, aims the tool 4 on a workpiece (not shown), and presses a switch (not shown). The compressed air flows through the air passage 205 via the air inlet in the handle body 1, and enters a rear side of the pressure chamber 203 so as to push forwardly the piston 3, which in turn, strikes a rear end of the tool 4 so that the tool 4 produces a hammering force on the workpiece. Meanwhile, the other hand of the operator presses a rear end of the upper portion 102 of the handle body 1 so as to maintain contact between the tool 4 and the workpiece.
Although the aforementioned conventional pneumatic hammer drill can achieve its intended purpose, since the upper portion 102 of the handle body 1 is not provided with a damping element at a rear end thereof, during hammering, an impact force between the tool 4 and the workpiece is transmitted to the operator's hands. Long-term exposure to such continuous hammering can lead to injuries of the operator's hands and wrists.